Natural or synthetic latex possesses favorable physical and rheological properties due to its soft elastic characteristics and high resistance to mechanical stresses and heat. Because of these desirable properties, latex is widely incorporated in a number of consumer goods and medical devices (e.g., condoms). Due to its hydrophobicity, however, latex is not compatible with blood, and can irreversibly adsorb proteins and platelets on its surface when in contact with biologics. Additionally, high frictional and abrasive forces can occur between the interface of latex-based medical devices and tissues, leading to discomfort, increased risks of infections, tissue damage, and pain for the user.
According to the World Health Organization, the lack of adequate lubrication remains a major drawback for proper and consistent condom use. The minimal amount of lubrication included with condoms during packaging is typically insufficient to maintain the condom's lubricity throughout intercourse. Consequently, partners will either (1) not use a condom and increase risks for unwanted pregnancies and spread of Sexually transmitted infections (STIs), or (2) use an inadequately lubricious condom resulting in mucosal microtrauma, pain, and decreased satisfaction between partners. This microtrauma and pain may arise from dramatically increased penetrative force during intercourse when lubrication is inadequate. Typical healthy vaginal lubrication has been reported to require a penetrative force of 0.5 kg, whereas a typical post-menopausal or poor vaginal lubrication requires a three-fold greater penetrative force of 1.5 kg. There is also a significant demand for better lubrication products and strategies to be used with condoms, particularly for older women in menopause and post-menopausal stages affected by vaginal dryness.
Silicone-based lubricants are the most commonly used lubricants today and are applied to both male and female condoms during the manufacturing process prior to packaging. Despite this, condom consumer satisfaction with condom lubricity remains low. Unfortunately, these unmet needs exacerbate the societal stigma and negative perception that condoms are uncomfortable and will decrease pleasure during intercourse, which adversely affects the consistency of proper condom usage.
A variety of methods have been explored to chemically or physically modify natural or synthetic latex to possess hydrophilic and lubricous properties, all with limited success. The different types of hydrophilic monomers that are compatible for polymerization reactions are currently limited. Surface modification strategies involving the application of hydrophilic coatings to the surface of latex-based substrates have proven to be challenging, for example, due to persistent delamination between the coating and latex.
Thus, there is an ongoing critical need to develop novel durable, flexible, non-toxic and low-costing hydrophilic coatings and application strategies that are compatible with natural and synthetic latex-based surfaces and medical devices, particularly for condoms.